Acceleration sensor

ABSTRACT

A sensor includes an operator mounted within a tubular guide for movement in one axial direction to an actuated position under a spring bias. The guide is mounted coaxially of a cylindrical support. A cylindrical seismic mass is slidable coaxially of the tube and support and is normally biased axially oppositely of the operator and against an end wall of the support by a coil compression spring seating against the other end wall of the support and a radial end wall of the mass. An annular retainer is slidable coaxially of the guide tube and includes an annular groove at one end thereof which includes a radial wall merging into an axial wall opening to a radial end wall of the retainer. A peripheral groove adjacent one end of the operator includes a conical wall located at a conical angle of approximately 60* to the axis of the operator. A plurality of balls are each freely received within a respective radial aperture of the guide tube and engage both the radial and axial walls of the retainer and the conical wall of the operator groove to detent the operator against movement. The retainer walls are spring biased into engagement with the balls by a coil compression spring seating on the other wall of the support and a radial flange at the one end of the retainer. The radial wall of the retainer is spaced a predetermined distance from the radial end wall of the mass. When an acceleration pulse of predetermined amplitude and time is applied coaxially of the mass, the movement of the mass engages the radial end wall of the mass with the radial wall of the retainer to move the retainer in the one axial direction and permit the balls to be forced outwardly of the retainer by the operator conical wall as the retainer axial wall moves axially and out of engagement therewith. This releases the operator. When the balls are released, they are received in an annular recess in the radial end wall of the mass.

United States Patent 51 May 16, 1972 Prachar [54] ACCELERATION SENSOR[72] Inventor: Otakar P. Prachar, Santa Barbara, Calif.

[73] Assignee: General Motors Corporation, Detroit,

Mich.

[22} Filed: Jan. 21, 1971 [2]] Appl. No.: 108,455

[52] U.S. Cl ..73/514 [51] Int. Cl. ..G01p 15/02 [58] Field ofSearch..73/492,514-517;

200/61.45 R, 61.53; 116/1 14 AH [56] References Cited UNITED STATESPATENTS 3,078,722 2/1963 Kongelbeck ..73/515 X 3,117,196 1/1964 Vincent..200/61.45 R

Primary Examiner-James J. Gill Attorney-W. E. Finken and Herbert Furman[5 7] ABSTRACT A sensor includes an operator mounted within a tubularguide for movement in one axial direction to an actuated position undera spring bias. The guide is mounted coaxially of a cylindrical support.A cylindrical seismic mass is slidable coaxially of the tube and supportand is normally biased axially oppositely of the operator and against anend wall of the support by a coil compression spring seating against theother end wall of the support and a radial end wall of the mass. Anannular retainer is slidable coaxially of the guide tube and includes anannular groove at one end thereof which includes a radial wall merginginto an axial wall opening to a radial end wall of the retainer. Aperipheral groove adjacent one end of the operator includes a conicalwall located at a conical angle of approximately 60 to the axis of theoperator. A plurality of balls are each freely received within arespective radial aperture of the guide tube and engage both the radialand axial walls of the retainer and the conical wall of the operatorgroove to detent the operator against movement. The retainer walls arespring biased into engagement with the balls by a coil compressionspring seating on the other wall of the support and a radial flange atthe one end of the retainer. The radial wall of the retainer is spaced apredetermined distance from the radial end wall of the mass. When anacceleration pulse of predetermined amplitude and time is appliedcoaxially of the mass, the movement of the mass engages the radial endwall of the mass with the radial wall of the retainer to move theretainer in the one axial direction and permit the balls to be forcedoutwardly of the retainer by the operator conical wall as the retaineraxial wall moves axially and out of engagement therewith. This releasesthe operator. When the balls are released, they are received in anannular recess in the radial end wall of the mass.

6 Claims, 2 Drawing Figures ACCELERATION SENSOR This invention relatesto sensors and more particularly to sensors of the type wherein anoperator is releasably held in unactuated position by a plurality ofdetent balls releasable upon a seismic mass receiving an accelerationpulse of predetermined amplitude and time.

One of the features of the sensor of this invention is that the operatoris mounted coaxially of a guide tube and biased in one axial direction,with the balls being held in detent engagement with a conical wall ofthe operator by an annular retainer mounted coaxially of the guide tubeand resiliently biased in an opposite axial direction to retain axialand radial walls thereof in engagement with the balls and preventmovement of the balls out of engagement with the conical wall of theoperator. Another feature of this invention is that the retainer ismoved axially of the balls to release the operator by impact with anannular seismic mass movable coaxially of the guide tube when a pulse ofpredetermined amplitude and time is applied generally axially thereof. Afurther feature of this invention is that the conical wall of theoperator engaged by the balls is located at a conical angle ofapproximately 60 to the axis of the operator to permit instantaneousmovement of the bails out of engagement therewith when the balls arereleased by the retainer. Yet another feature of this invention is thatthe axial wall of the retainer terminates at a radial end wall of theretainer impacted by a radial end wall of the mass when the mass movesunder the acceleration pulse of predetermined amplitude and time. Yet afurther feature of this invention is that the radial end wall of themass includes a recess which receives the balls when the balls arereleased by the retainer.

These and other features of the sensor of this invention will be readilyapparent from the following specification and drawings wherein:

FIG. 1 is a view of the sensor in unactuated position; and

F IG. 2 is a view of the sensor in actuated position.

Referring now particularly to FIG. 1 of the drawings, a sensor accordingto this invention includes a support 12 comprised of a cylindricalhousing 14 having a closed one end wall 16 and another end wall 18centrally apertured at 20. A hollow cylindrical guide tube 22 extendsbetween walls 16 and 18, with one end of the tube receiving acylindrical embossment 24 of wall 16 and the other end of the tube beingsuitably secured to wall 18 and opening coaxially of the opening 20. Acylindrical seismic mass 26 of predetermined weight is slidably mountedon the guide tube 22 for movement coaxially thereof. The mass 26 isguided both by the guide tube and by the inner wall of housing 14. Acoil compression spring 28 of predetermined strength surrounds the guidetube 22 and seats between the wall 18 of housing 14 and a recessedradial one end wall 30 of mass 26. Spring 28 holds an opposite end wall32 of the mass 26 in engagement with wall 16 to locate the mass in apredetermined position axially of guide tube 22. The mass 26 furtherincludes a cylindrical recess 34 which opens both axially of the wall 30and radially of the guide tube 22.

A cylindrical operator 36 is coaxially mounted within the guide tube 22for movement between its unactuated position shown in FIG. 1 and itsactuated position shown in FIG. 2 wherein a pointed end 38 of theoperator projects through the opening 20 for engagement with adetonator, or a switch, or a diaphragm of a sealed pressure vessel for apurpose to be hereinafter explained. A coil compression spring 40 seatsbetween the embossment 24 of wall 16 and the shouldered other end of theoperator 36 to bias the operator to its actuated position. A peripheralgroove 44 adjacent one end of the operator 36 includes an arcuategenerally radially extending wall 46 which merges into a generallyradial or conical wall 48 formed on a conical angle of preferably 60 tothe axis of the operator. The guide tube 22 includes a plurality,preferably three or four, of radial apertures 50 each of which freelyreceives a ball 52. The radial wall 46 of the groove 44 conforms to thetangential periphery of the balls 52.

A cylindrical retainer 54 is slidable coaxially of the guide tube 22. Aradial peripheral flange 56 at one end of the retainer seats one end ofa coil compression spring 58, the

other end of which seats on wall 18. Spring 58 is coaxial of springs 26and 40 and of the guide tube 22 and is of less strength than spring 40.The one end of the retainer 54 includes a cylindrical recess comprisedof a generally radially extending arcuate wall 60 which merges into agenerally axially extending wall 62 of predetermined length terminatingat the radial end wall 64 of the one end of the retainer. Wall 64 isspaced a predetermined axial distance from wall 30. As shown in FIG. 1,the tangential engagement of the balls 52 with the conical wall 48 ofthe operator and the radial and axial walls 60 and 62 of the retainer 54under the opposing biases of the springs 40 and 58, normally detents theoperator 36 in its unactuated position.

The spring 28 normally applies a force to the seismic mass 26 such thatno movement of the mass can occur unless a load of approximately 2 to 3Gs is applied thereto generally coaxial of the mass and of the guidetube 22. When a load exceeding this lower limit is received by the mass26, the mass will, of course, move to the left as viewed in FIG. 1. Whenthe load exceeds an upper limit, such as 8 Gs for a predetermined timein ms, the wall 30 of the mass 26 impacts the wall 64 of the retainer 54and moves with the retainer to the left against the bias of spring 58 asshown in FIG. 2. When the its 54 moves to the left through what may betermed the integrating distance, that is, the axial extent of wall 62,the balls 52 will be released from the openings 50 and from axial wall62 into the recess 34 of mass 26 to release the operator as shown inFIG. 2. The mass 26 will move with the balls 52 and the retainer 54 as aunit to the left as viewed in FIG. 2 until such time as the pulse hasdecayed to a lower limit whereupon the springs 58 and 28 return the mass26 to its position shown in FIG. 1 and likewise hold the retainer 54 inengagement with the wall 30 of the mass to hold balls 52 in recess 34.

The balls 52 are forced out of the openings 50 and into the recess 34 bythe action of the spring 40 and the camming action of wall 48 when theballs are released by retainer 54. The conical shape of wall 48 preventsany locking of the balls in the groove 44 when the balls are released bythe retainer. It should also be noted that it is possible for the mass26 to impact the retainer 54 and move the retainer through a distanceless than the integrating distance if the impulse on the mass is appliedfor less than the predetermined time. The shape of wall 48 aids theretainer in returning to its position shown in FIG. 1.

If desired, the retainer 54 can be reversed end for end so that flange56 is at the left-hand end of the retainer rather than the right-handend as shown. The cylindrical recess of the retainer will then belocated in the right-hand end of the retainer and recess 34 will beaxially deepened so that wall 30 of the mass can engage flange 56 whenthe mass is subjected to an acceleration pulse of predeterminedamplitude and time.

As previously mentioned, the pointed end 38 of the operator 36 mayengage various members or mechanisms. The sensor of this invention isspecifically intended for use with an inflatable cushion as part of avehicle body occupant restraint system. Such a system includes aninflatable bag or cushion and a manifold connecting the cushion with apressure vessel containing fluid under pressure, or such a pressurevessel containing both fluid and pyrotechnic material, or with apyrotechnic gas generator. The detonator actuated by the operator may,for example, rupture the diaphragm of the sealed pressure vessel, or theoperator may close the switch to initiate rupture of such diaphragm, orclose a switch to initiate the pyrotechnic reaction.

Thus, this invention provides an improved sensor.

lclaim:

1. A sensor comprising, in combination, a support, a generally tubularaxial guide mounted on the support and including a plurality of radialapertures, an annular seismic mass mounted coaxially of the guide formovement relative thereto, means exerting a predetermined bias on themass in one axial direction, means on the mass and support locating themass in a predetermined axial position with respect to the guide, an

operator mounted coaxially of the guide and including a generallyannular radial wall, means exerting a bias on the operator in theopposite axial direction, an annular member mounted coaxially of theguide for movement relative thereto and including an annular radial wallmerging into an annular axial wall of predetermined extent spacedradially of the guide, means exerting a bias on the annular member inthe one axial direction, a plurality of balls, each freely received in arespective aperture of the guide and engaging the radial wall of theoperator and the radial and axial walls of the annular member under theoperator and annular member bias means to hold the operator againstmovement in the other axial direction, the application of a generallycoaxial acceleration pulse of predetermined amplitude and time to themass moving the mass in the other axial direction against the biasthereon to impact the annular member and move the annular member in theother axial direction, movement of the annular member moving the axialwall thereof out of engagement with the balls to release the balls fromthe annular member and from the operator to release the operator formovement under the bias thereon.

2. A sensor comprising, in combination, a support, a generally tubularaxial guide mounted on the support and in cluding a plurality of radialapertures, an annular seismic mass mounted coaxially of the guide formovement relative thereto and including a radial end wall having anannular recess opening axially therethrough, means exerting apredetermined bias on the mass in one axialdirection, means on the massand support locating the mass in a predetermined axial position withrespect to the guide, an operator mounted coaxially of the guide andincluding a generally annular radial wall, means exerting a bias on theoperator in the opposite axial direction, an annular member mountedcoaxially of the guide for movement relative thereto and including anannular radial wall merging into an annular axial wall of predeterminedextent spaced radially of the guide and terminating at one end of theannular member, means exerting a bias on the annular member in the oneaxial direction, a plurality of balls, each freely received in arespective aperture of the guide and engaging the radial wall of theoperator and the radial and axial walls of the annular member under theoperator and annular member bias means to hold the operator againstmovement in the other axial direction, the application of a generallycoaxial acceleration pulse of predetermined amplitude and time to themass moving the mass in the other axial direction against the biasthereon to impact the annular member and move the annular member in theother axial direction, movement of the annular member moving the axialwall thereof out of engagement with the balls to release the balls fromthe annular member and from the operator wall to release the operatorfor movement under the bias thereon, the mass recess opening to the oneend of the annular member upon release of the balls for receipt thereof.

3. A sensor as recited in claim 2 wherein the one end of the annularmember includes a generally radially extending flange impacted by theradial end wall of the mass to release the balls from the annularmember.

4. A sensor as recited in claim 3 wherein the bias means for the annularmember includes a compression spring seating on the support and theradial flange of the annular member.

5. A sensor as recited in claim 2 wherein the seismic mass and annularmember move as a unit after impact, and the biasing means respectivethereto move the unit in the one axial direction upon decay of theacceleration pulse below the predetermined amplitude and time. a

6. A sensor comprising, in combination, a support, a generally tubularaxial guide mounted on the support and including a plurality of radialapertures, an annular seismic mass mounted coaxially of the guide formovement relative thereto and including a radial end wall having anannular recess opening axially therethrough, means exerting apredetermined bias on the mass in one axial direction, means on the massand support locating the mass in a predetermined axial position withrespect to t e guide, an operator mounted coaxially of the guide andincluding a generally radially opening peripheral groove having aconical wall generated about the axis thereof, means exerting a bias onthe operator in the opposite axial direction, an annular member mountedcoaxially of the guide for movement relative thereto and including anannular radial wall merging into an annular axial wall of predeterminedextent spaced radially of the guide and defining therewith a recessopening to the seismic mass recess, means exerting a bias on the annularmember in the one axial direction, a plurality of balls, each freelyreceived in a respective aperture of the guide and engaging the conicalwall of the operator and the radial and axial walls of the annularmember to hold the operator against movement in the other axialdirection, the application of an acceleration pulse of predeterminedamplitude and time to the mass moving the mass in the other axialdirection against the bias thereon to impact the annular member and movetherewith in the other axial direction, movement of the annular membermoving the axial wall thereof out of engagement with the balls torelease the balls for movement into the recess in the radial wall of themass.

1. A sensor comprising, in combination, a support, a generally tubularaxial guide mounted on the support and including a plurality of radialapertures, an annular seismic mass mounted coaxially of the guide formovement relative thereto, means exerting a predetermined bias on themass in one axial direction, means on the mass and support locating themass in a predetermined axial position with respect to the guide, anoperator mounted coaxially of the guide and including a generallyannular radial wall, means exerting a bias on the operator in theopposite axial direction, an annular member mounted coaxially of theguide for movement relative thereto and including an annular radial wallmerging into an annular axial wall of predetermined extent spacedradially of the guide, means exerting a bias on the annular member inthe one axial direction, a plurality of balls, each freely received in arespective aperture of the guide and engaging the radial wall of theoperator and the radial and axial walls of the annular member under theoperator and annular member bias means to hold the operator againstmovement in the other axial direction, the application of a generallycoaxial acceleration pulse of predetermined amplitude and time to themass moving the mass in the other axial direction against the biasthereon to impact the annular membEr and move the annular member in theother axial direction, movement of the annular member moving the axialwall thereof out of engagement with the balls to release the balls fromthe annular member and from the operator to release the operator formovement under the bias thereon.
 2. A sensor comprising, in combination,a support, a generally tubular axial guide mounted on the support andincluding a plurality of radial apertures, an annular seismic massmounted coaxially of the guide for movement relative thereto andincluding a radial end wall having an annular recess opening axiallytherethrough, means exerting a predetermined bias on the mass in oneaxial direction, means on the mass and support locating the mass in apredetermined axial position with respect to the guide, an operatormounted coaxially of the guide and including a generally annular radialwall, means exerting a bias on the operator in the opposite axialdirection, an annular member mounted coaxially of the guide for movementrelative thereto and including an annular radial wall merging into anannular axial wall of predetermined extent spaced radially of the guideand terminating at one end of the annular member, means exerting a biason the annular member in the one axial direction, a plurality of balls,each freely received in a respective aperture of the guide and engagingthe radial wall of the operator and the radial and axial walls of theannular member under the operator and annular member bias means to holdthe operator against movement in the other axial direction, theapplication of a generally coaxial acceleration pulse of predeterminedamplitude and time to the mass moving the mass in the other axialdirection against the bias thereon to impact the annular member and movethe annular member in the other axial direction, movement of the annularmember moving the axial wall thereof out of engagement with the balls torelease the balls from the annular member and from the operator wall torelease the operator for movement under the bias thereon, the massrecess opening to the one end of the annular member upon release of theballs for receipt thereof.
 3. A sensor as recited in claim 2 wherein theone end of the annular member includes a generally radially extendingflange impacted by the radial end wall of the mass to release the ballsfrom the annular member.
 4. A sensor as recited in claim 3 wherein thebias means for the annular member includes a compression spring seatingon the support and the radial flange of the annular member.
 5. A sensoras recited in claim 2 wherein the seismic mass and annular member moveas a unit after impact, and the biasing means respective thereto movethe unit in the one axial direction upon decay of the acceleration pulsebelow the predetermined amplitude and time.
 6. A sensor comprising, incombination, a support, a generally tubular axial guide mounted on thesupport and including a plurality of radial apertures, an annularseismic mass mounted coaxially of the guide for movement relativethereto and including a radial end wall having an annular recess openingaxially therethrough, means exerting a predetermined bias on the mass inone axial direction, means on the mass and support locating the mass ina predetermined axial position with respect to the guide, an operatormounted coaxially of the guide and including a generally radiallyopening peripheral groove having a conical wall generated about the axisthereof, means exerting a bias on the operator in the opposite axialdirection, an annular member mounted coaxially of the guide for movementrelative thereto and including an annular radial wall merging into anannular axial wall of predetermined extent spaced radially of the guideand defining therewith a recess opening to the seismic mass recess,means exerting a bias on the annular member in the one axial direction,a plurality of balls, each freely received in a respective aperture ofthe guide and engaging the conical wall of the operaTor and the radialand axial walls of the annular member to hold the operator againstmovement in the other axial direction, the application of anacceleration pulse of predetermined amplitude and time to the massmoving the mass in the other axial direction against the bias thereon toimpact the annular member and move therewith in the other axialdirection, movement of the annular member moving the axial wall thereofout of engagement with the balls to release the balls for movement intothe recess in the radial wall of the mass.